Field-magnet and winding for electrical machines.



C. H. SMUOT.

FIELD MAGNET AND WINDING FOR ELECTRICAL MACHINES.

APPLIQATION FILED 23.10, 1907. RENEWED JUNE 22,1912.

1,054,047, catented Feb.

Inventor:

har/@645 15ml? CUM/2655 e5 UNITED STATES PATENT OFFICE.

CHARLES H. SMOOL OF CHICAGO, ILLINOIS, ASSIGNOR TO RATEAU TURBINE COM- PANY, OF CHICAGO, ILLINOIS, A CORPORATION OF WEST VIRGINIA.

FIELD-MAGNET AND WINDING FOR ELECTRICAL MACHINES.

Specification of Letters Patent.

Patented Feb. 25,1913.

Application filed February 16, 1907, Serial No. 357,664. Renewed June 22, 1912 Serial No. 705,311.

To all whom it may concern Be it known that I, CHARLES H. Siroor,

citizen of theUnited States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Field-Magnets and Vindings for Electrical Machines, of which the following is a full, clear, concise, and exact description.

My invention relates to dynamo electric machines such as generators and motors, with particular reference to dynamos of the direct current type.

The object is to pro ide an improved field magnet structure and an organization of windings therefor, such that the armature reaction upon the field will be compensated for, and sparkless commutation secured: while the structure is simple, easily built and assembled and convenient in arrangement.

The invention is illustrated in the act-ompanying drawing, which is a diagram illustrating the magnetic structure and electrical organization of a four-pole generator provided with commutating-poles intermediate the main poles.

The armature l rotates in the magnetic field established by the four pole-pieces N, N, S, S, which project inwardly from the fieldunagnet frame 2. Brushes 3, l. 5 and (3 bear upon the commutator (indicated by the circle 7); and while these brushes are located in radial line with the main field poles. it will be understood that the armature winding is of the usual modern type in which the leads to the comn'iutator are diagonally disposed, the segments upon which the brushes rest being connected with armature coils located at the neutral points approximately midway between the main field. poles. in other words, when a given armature coil is undergoing commutation by the brush resting upon the corresponding commutator-segments forming the terminals of such coil, it is in the act of prising from the influence of one field pole to the influence of the succeeding pole. Commutating poles 8, 9, 10 and 11 are provided upon the field magnet, facing the armature at points midwa between the main poles to act upon the col s undergoing commutation. These commutatihg poles are for the purpose of build pose of compensating for the variation in the armature magneto-motive force under the face of the ctunmutating pole.

The field magnet is compound-wound, the shanks of the main field pole pieces carrying shunt coils 14 and series coils 15. The pole pieces are constructed with forked ends or tips facing'the armature, the faces thereof being comparatively broad so as to span a large arc the armature surface; and the prongs or tips of these main poles are pro- Yidedfw'ith individual compensating coils 16 not embracing the couunututing poles but acting to approximate correct the distorting eitect of the armature reaction across the pole faces.

In the machine shown in the drawing, the circuit may be traced from the positive brushes 3 and 5 which are connected together, through a conductor 1? divided into two parallel branches each which branches includes in Sen coils l6 and shadin coil chine: th said in no =5 tor 155 which leads thrc coil; 12 of the commute ng connects to a conductor 19, which extends through the series coils 15 of the main poles to the conductor of the external circuit. The return conductor 52!) from the external circuit is connected direct to brushes 4 and ii or" the machine rection of current ticw in the Various conductors is further indie: ted by arrows. Connections are also snown whereby a resistance 21 can be included in shunt of the compensating windings l2, and whereby a resistance :22 can be included in shunt of the "main series field windings 15, to adjust the strength of the currents in these Windin poles and then respelctively. The sip windings 14.-

the

main poles are connected across the termi nals of the machine, in series with a binding'post 23 and an adjustable resistance 24.

It is well-known that in an ordinary direct current generator, the current, flowing in the armature tends to magnetize the latter along an axis at an angle to the ma netizing efiect of-the field poles, the resut creases or decreases.

In accordance with my invention, the field magnetpole is providedwith separate tips or prongs about which individual compensating coils 16 are provided, these coils being connected in serieswith the armature so that the current-therein will vary with the armature current, the direction of winding and number of ampere turns being such that the magneto-motive force set up by the. compensating coils will oppose and approximately balance the cross-magnetizing effect of the neighboring armature conductors lying under such pole. The field distortion above described is thus corrected for all con-- 4 ditions of load.

I am aware that it has been proposed heretofore to provide large fiat pan-cake compensating coils spanning the entire distance from one pole to the next and also located midway between the field poles; but

such large coils are very expensive, requiring long reaches of copper for end-connections, and "being very difiicult to apply and mechanically support, while in case repair or adjustment becomes necessary, much la-' bor'is involved in removing and replacing the windings. In the arrangement of my invention, the compensating coils, being individual to and surrounding only the mere prongs of the pole tip, are small in size and require only the minimum amount of'cop- 'per. My coils are thus easily Wound and replaced, readily connected in their appropriate circuit, accessible in position and easily removed and replaced in case" of repair or adjustment. Each compensating coil may, furthermore, be especially adapted to meet the conditions of" the individual pole piece on which it is mounted, instead of being commonto two pole-pieces. A further advantage of myinvention' is that the magnetic structure 1 comprises separate salient pole.'pieces"for the main and commutating poles which are-given any desired proportion's independent of each other andare energized by independent coils, so that they may be worked at different degrees of saturation.

This is desirable because the main field poles should be highly saturated so as not to vary in strength too greatly with slight changes in voltage of their excitingcurrent,

while the magnetic strength of the commutating poles on the other hand should respond directly to chan es in the armature current,to meet and ba ance the cross-magnetizingeflectof the latter,

My invention also contemplates the pro vision of independent shading coils '13 upon the commutating poles in addition to the energizing coils 12. "lhe last-mentioned coils act to provide a'total average flux from the commutating. ole sufiicient'to' vneutralize the effect of sel' -induction in the coils undergoing commutation. The shading coils 13 on the other hand, serve to govern the vdistribution of this total net,

or average fluizfv so thatit' will not be unduly distorted by thearmature reaction. The current flowing in the armature conductors in the immediate neighborhood of v the commutating poles has a'reactive efiect upon the flux from such poles similar to that which it has upon the main'poles, this eifect varying with the strength of the armature current as the latter changes underv variations of load. In accordance with my invention, the shading coils 13 are provided upon the prongs or tips of the commutating poles and connected in series with the armature, these coils being proportioned and wound so that their magnetic effect will oppose and approximately balance the reactive magnetic vefi'ect of the current in the neighboring armature conductors. By

this means, distortion of the average flux from the commutating poles is prevented,

.and this flux is caused to be distributed in the most effective manner to neutralize the self-induction in this coils undergoing commutation, such distribution being substantially unaflected by changes in the load conditions.

Inthe drawings is shown the equalizing connection 25 commonly used in connecting compound dynamos in parallel.

I claim l. The combination with a dynamo having-a field magnet system comprising main poles and intermediate cgmmutat-ing poles,

said commut-ating poles being made up of subdivided polar projections, of means for exciting the main poles to a'high degree of saturation, means for magnetizing the oommut-ating poles to a low degree of saturation, varying in intensity with the armature current, and a shading coil individual to and surrounding a portion of each commutating pole, adapted to govern the distribution of the fiuxfrom such pole.

2. In an electrical machine, the combination with a field magnet, system compris ing a yoke, main pole-pieces and intermediate commutating pole-pieces, said main polepieces having separate pron s or tips, of a main winding. upon each fie d ma et core, compensating windings individua to and immediately surrounding the prongs of the main pole-pieces, separate windings individual to and immediately surrounding the commutating poles, and shading coils at the tips of the commutating poles, said compensating windings and shading coils being connected in series with the armature circuit,

3. In an electrical machine, the combination with the armature, of a field magnet system comprising a yoke, main polepieces and intermediate commutating pole-pieces upon said yoke, said commutating poles being made up of subdivided polar projections, main and compensating field windings, and shading coils individual to and immediately surrounding fractional rtions of the commutating poles adapte to govern the local distribution of the flux from said last-mentionedpoles.

' 4c. In a magnetic system for dynainos, the combination With main poles and commutating poles, of compensating coils individual to the main poles, independent energizing coils for said commutating poles, and shading coils governing the local distribution of flux from said connnutating poles.

5. In a magnetic system for dynamos, the combination with main poles and commutating poles and energizing windings therefor, of independent shading coils on the tips of the commutating poles acting to compensate for armature reaction upon said last-mentioned poles.

6. In a dynamo-electric machine, the combination with an armature and main ,field poles, of a commutating polehaving a relatively Wide face, a main exciting Winding adapted to provide an average magneto-motive force over said commutating pole face, and an auxiliary Winding embracing a portion of said cpmmutating pole face and adapted to compensate for variations in the magneto-motive force of the armature coils under said commutating pole.

In Witness whereof, I, hereunto subscribe my 7name this 13th day of February A. D., 190

CHARLES H. SMOOT.

Witnesses:

GEORGE P. BARTON, GnononE. FOLK. 

